1. Field of the Invention
The present invention relates to an image forming apparatus such as a printer, a photocopying machine, or a printing unit of a facsimile machine or of a multi-function device. More particularly, the present invention relates to an image forming apparatus of the type which incorporates a removable process cartridge including a photosensitive drum together with associated components necessary for electrophotography.
2. Description of the Related Art
Typically, a prior art image forming apparatus such as a printer or a photocopying machine incorporates various electrophotographic components (e.g. a photosensitive drum, a toner cartridge) in a single module called "process cartridge" for facilitating replacement. In operation, recording papers are successively guided to pass through the process cartridge for printing by transferring toner images on the photosensitive drum to the recording paper.
With the image forming apparatus of the type described above, a paper jam sometimes occurs if a recording paper is warped or if a plurality of recording papers erroneously supplied to the process cartridge at the same time. For eliminating such a paper jam, the user need to first remove the process cartridge from the machine body and then remove the jammed paper from the process cartridge. After elimination of the paper jam, the process cartridge may be reloaded into the machine body.
The need for eliminating the paper jam and for reloading the process cartridge may cause the following problems.
At the time of removing the jammed paper, the process cartridge may be electrostatically charged due to friction, and the amount of the electrostatic charge increases with an increase of the paper clamping force exerted between the photosensitive drum and a paper feed roller. However, no measure has been conventionally taken to preliminarily remove the electrostatic charge from the process cartridge at the time of reloading it into the machine body.
On the other hand, the process cartridge is provided with a first group of connection terminals for power supply and grounding, whereas the machine body is provided with a second group of connection terminals for the same purposes. Thus, when the process cartridge having been previously charged electrostatically is reloaded into the machine body, an abrupt discharge may occur when the first group connection terminals approach the second group connection terminals, which may cause damage to the electronic circuitry of the image forming apparatus and/or malfunction of the circuitry. Further, even if an abrupt discharge does not occur, the electrostatic charge will ultimately flows into the electronic circuitry, thereby adversely affecting the circuitry.